Geometry Chart

If you feel like you've got too much on your head when you're riding, try a lighter helmet. Giro's Prolight helmet is a race-level helmet that presents the new standard for lightweight and streamlined design. It has a superlight In-Mold shell with 25 aerodynamic vents to channel maximum airflow over your head. It also sports the Roc Loc SL fit system with Super Fit sizing, so you create a fit that is so custom, you'll barely feel the helmet at all.

In-Mold construction provides strength, integrity and is so lightweight, you'll have to remind yourself that you've got a helmet on at all

25 Wind Tunnel vents with fully optimized internal channels thrust cool, fresh air over and around your head while forcing heat and stale air out

I was hit by a car while riding my road bike wearing this helmet. The helmet cracked and my head did not. I sustained a concussion but if this were a lesser helmet I believe things would have been much worse. I purchased this as a replacement for the cracked one.

It does in fact adjust, though not on the fly. Buy the appropriate size. There are three different holes on each side of the inside of the helmet in which to anchor the sizing straps. I've had used the different holes for when my hair is short, or when I'm wearing a cap. It fits. It works. It's not as adjustable as a "regular" helmet, but it's so much lighter than helmets with mechanisms, it's worth it. I usually forget that I'm wearing it.

I purchased this helmet for my husband. He is an active road cyclist. The helmet was light weight as indicated. However, the fore/aft system adjustment was very flimsy and looked like it would not be very durable for regular riding. We returned it.

As I've seen in other reviews, this helmet felt "tippy" on my head, and didn't feel secure. I wanted the feeling of "it feels like there's nothing on your head", and it is very very light. I was ready for the very spare adjustment system, but it just didn't give me a feeling of security. My head measures 23.25" which I thought would give me a nice close fit with the Medium. It fit front to back, but with gaps around the the sides. For some who happen to have the right shaped head, they might like it, but it wasn't for me. I think the new Giro Aeon (slightly heavier) might have worked out these problems, but it's really expensive. For now, I'm going back to my trusty old Giro Transfer that I got years ago for twenty bucks (yes, TWENTY BUCKS!!). Being a low cost helmet, it comes as a "one size fits all", but for me it's a better fit. Despite the little bit of extra weight, it was almost a relief to put on after trying to get comfy with the Prolight. I reluctantly sent the Prolight back.